Saw teeth for circular saws of the type mounted on a feller head for a tree felling apparatus are known. U.S. Pat. No. 4,932,447, Morin, 1990, and U.S. Pat. No. 5,205,199, MacLennan, 1993, represent saw teeth that have become well known in the industry. Morin '447 and MacLennan '199 both teach a replaceable saw tooth with four sides. The teeth can be rotated when the active cutting tips and edges become dull or worn.
Saw teeth wear relatively quickly and may become rounded or dull. This may cause increased fuel consumption, decreased productivity, or poor cut quality, or all of them, and may tend to result in a need for maintenance. The cutting tips do the majority of the cutting of the tree fibers and even though the teeth may have large cutting tips, only a small area at the end of the tip is used. As the tip wears it may tend to become rounded and the tooth body immediately behind the end of the tip may then present the outermost part of the tooth.
Good design of saw teeth have the front or leading cutting edges of the tooth as the widest part of the tooth so that the leading cutting edge can cut the tree fibers and the trailing part of the tooth is tapered so that the tooth surface is relieved behind the leading cutting edges so the trailing part of the tooth doesn't contact the tree and cause friction and loss of energy of the saw blade. FIGS. 1a-1f, and, in particular FIGS. 1e and 1f, show a prior art tooth in both new and worn conditions.
The width of the saw cut or dimension at the widest part of the leading cutting edge is called the kerf. As conventional saw teeth wear, the leading cutting edges tend to become rounded and the tooth body immediately behind the leading edge may then be the thickest part of the tooth. See FIG. 1f. When cutting with a dull conventional saw tooth as described above, the narrower cutting tips cut an initial kerf and the thicker trailing tooth body has to be pushed through the initial kerf of the tree as the blade feeds through the tree, pushing and tearing the tree fiber above and below the initial kerf to create a wider final kerf equal to the width of the trailing tooth body thereby causing increased friction and loss of blade energy. This may tend to consume more energy, decrease machine productivity and produce a rougher cut on the tree butt. A dull tooth may impose higher forces and stresses on the saw blade than a sharp tooth.
Conventional four-sided rotatable saw teeth have cutting edges are planar (that lie in one plane). See FIG. 1a. While these conventional saw teeth are easy to manufacture, as they wear the tend to become dull and rounded as described above. The width of the leading cutting edge portion of the tooth body is worn thinner than the tooth body behind the leading edge causing increased friction, inefficient cutting and excessive loss of blade energy which results in more fuel being consumed.